On 22 Apr 2002 at 0:08, Ben Laurie wrote: > > Yes. If you know what PRNG somebody is using and you know the > > seed you know the output. Seems to me the best a PRNG > > could hope to get is a situation where, looking at a long stream > > of output, there's no way of predicting the future output that's > > more efficient than guessing the initial seed. I don't think > > achieving that is all that hard in practice. > > Oh surely you can do better than that - making it hard to guess the seed > is also clearly a desirable property (and one that the square root "rng" > does not have). >
To me choosing the seed and the mathematics of a PRNG are conceptually separate. The seed of the square root prng is only "easy to guess" if you assume it's a small number. Of course, finding the square root of a 100 digit number to a precision of hundreds of decimal places is a lot of computational effort for no good reason. BTW, the original poster seemed to be under the delusion that a number had to be prime in order for its square to be irrational, but every integer that is not a perfect square has an irrational square root (if A and B are mutually prime, A^2/B^2 can't be simplified). George > Cheers, > > Ben. > > -- > http://www.apache-ssl.org/ben.html http://www.thebunker.net/ > > "There is no limit to what a man can do or how far he can go if he > doesn't mind who gets the credit." - Robert Woodruff
